Communication system



Sept. 1, 1936. W. s. LEMMON COMMUNICATION SYSTEM Filed 001;. 27, 1934 2 Sheets-Sheet 1 AMPLIFIER j\ (b) v jNVZNTOR. i /l\ BY a. WA TTORNEY w. s. L EMMON 2,053,092

COMMUNI CATION SYSTEM Sept. 1, 1936.

Filed Oct 27, 1954 2 Sheets-Sheet 2 nan llll

flMPL/F/ER RECE/ VER FIE-3.3.

UNIT R-1 l I I I PRINT/N6 TIME R? UNIT R-Z B C INVENTOR.

BY W7 A TTORNEY Patented Sept. 1, 1936,

NED STATES PATENT OFFICE 2.05am COMMUNICATION svsrsm Application October 27, 1934, Serial No. 750,257

6 Claims.

This invention relates to communication systems for the transmission and reception of character signals, and more particularly to multiplex telegraphy whereby a plurality of messages are transmitted simultaneously from a station and received simultaneously at another station either by line or radio.

The present invention will be explained in conjunction with a single impulse synchronous system and is particularly adaptable to this type of system, in which the dilferent characters to be transmitted and received are represented by single impulse signals which are definitely allocated during particular timed intervals.

Transmission of a plurality of messages simultaneously from one station to another remote thereto has been accomplished commercially in conjunction with the five unit code printing telegraph systems'. It will be shown hereinafter how the principle of the simultaneous transmission of a plurality of messages by the present invention difiers from the similar transmission of a plurality of messages by the five unit code systems.

Briefly, in the five unit code systems a given unit of time is divided into five intervals during each of which either positive or negative current may be transmitted to operate selecting and printing mechanisms accordingly.

Let it be assumed for illustrative purposes, solely, that the above said unit of time divided into five equal intervals is equivalent to one-fifteenth of a second. Therefore it is understood that this interval of time, one-fifteenth of a second, is the amount of time necessary to transmit a single character.

As mentioned previously, broadly, the printing telegraph system embodied in the present invention involves the shifting of the character impulse along the axis of a timed scale, the position of the impulse thereon determining the character to be selected. Now let it be assumed, again for illustrative purposes solely, that the operation of the printing telegraph unit requires onefifteenth of a second. It is obvious that the maximum limit of transmission in this theoretical system is fifteen characters per second. Again assuming that it requires but one-three hundredth of a second to send the character impulse in the single impulse system, it is evident that the difference in time required to transmit the character impulse and the time required for the recording unit to operate to effect transmission or reception of the character impulse is a definite interval of time that remains unused when this particular type of system is used for simplex operation.

It is therefore proposed, and an object of this invention, to employ this unused definite interval of time for the transmission of other similar character impulses, that is during the approximately one-fifteenth of a second period to transmit from a separate and detached printing unit or units character impulses during this spare period of time, or stated in a different manner, it is an object of the present invention to provide means for the transmission of a plurality of character signals from separate printing telegraph units during the timed interval required for sending one character signal during simplex operation.

It is a further object of this invention to transmit a character impulse from one printing unit while another printing unit is effecting the transmission or reception of another character impulse. 1

A still further object is the provision for th above mentioned multiplex transmission on the same frequency or with impulses or signals of the same characteristics. I

A still further object is to provide for multi plex transmission with a simplified arrangement of the transmitting and receiving equipment and the corresponding circuits.

A still further object is to provide for duplex operation on the same frequency or with impulses or signals of the same characteristics.

Various other objects and advantages of my invention will be obvious from the following particular description of one form of mechanism embodying the invention or from an inspection of the accompanying drawings; and the invention also constitutes certain new and novel features of the construction and combination. of parts .hereinafter set forth and claimed.

In the drawings:

Fig. 1 shows schematically a system by means of which the invention may be carried out.

Fig. 2 is an illustrative time graph of the character impulses.

Fig. 3 is an illustrative time graph showing relative operative positions of time receiving units. in the system.

Fig. 4 shows schematically a system by means of which the invention is applied to duplex operation.

Referring now to the drawings in which similar parts are designated by the same numerals in the several views, it is believed that a clear understanding of the invention will be had therefrom General description The type of single impulse printing telegraph system embodied in this invention is fully disclosed in the copending application Serial No. 710,614 filed February 10, 1934 by W. S. Lemmon, et al. and therefore it will be sufficient to disclose the following brief description of its operation.

Referring now to Fig. 1 the transmitting telegraph units T-l and T2 are similar units and likewise receiving units Rr-l and Rr-Z are similar so that a description of the operation of one combination will be adequate. In the figure TI represents a printing telegraph unit which may be of any well known type having a series of character pivoted key bars I0 and is adapted to initiate a character impulse when the character key is depressed and released. A separate contact l I is associated with each individual key bar l0 and connected to contact or segments I2 corresponding to the character represented by each key bar.

Rotary arm [3 driven by any suitable means, preferably a motor as indicated by designation M, is adapted to engage the contacts l2 in rather rapid succession to initiate the character pulse by completing the individual condenser charging circuit coacting with the transmitting commutator I5. An individual condenser I6 is provided for each character key bar I0, and is discharged by depressing the key 10 to engage contact ll to short circuit the said condenser. Charging of the condenser occurs during a predetermined interval of time when the rotary arm l3 engages the particular character segment I2, and when the corresponding depressed key bar is released to its normal position to engage contact ll thereby completing the charging circuit mentioned above, so that the drop across resistor l8 activates the connected sending circuit l9 and transmitting apparatus 20, as a result of which an impulse is transmitted at a particular moment during a predetermined timed interval.

The character impulse as initiated by the printer transmitter units in the manner just explained and transmission thereof effected by the wave transmitter either over a radio or line network in the usual manner is received in a well known manner by the wave receiver equipment 2|. The received impulse is then passed to the receiving commutator or distributor 22 and the printing telegraph receiver unit in a manner fully disclosed in the aforesaid application to record the character corresponding to the character pulse transmitted. It is understood that the r0- tary arm 23 rotated by suitable means such as a motor indicated at 24 is maintained in synchronism with the rotating arm l3 of the transmitting distributor l5 by methods well known in the art and one of which is disclosed in the said mentioned application.

It is understood by those skilled in the art how the synchronous distributors are used and may be applied to this type of system to effect the correct selection of the type bar 25 of unit R-l which is depressed upon energization of the solenoid 26, and each character solenoid attached to a key bar 21 which in turn is connected to the distributor segments or contacts 28, and therefore needs no further explanation.

Operation It has been mentioned above that the.transmitting unit T2 and the corresponding receiving unit R2 operate in the same manner as that described for the units T-l and Ri (Fig. 1). It was also mentioned above that the said units require a definite interval of time to effect their respective operations, namely, the initiating of the transmission of the character impulse and recording of the character corresponding to said impulse.

Let it be assumed in a simplex system that the rotary arm I3 is driven by its motor M at a speed of 900 R. P. M. or 15 R. P. S. If a timed period of one-fifteenth of a second is required for the printing telegraph unit to function it is obvious that it is possible to send but one character impulse during the single revolution of the rotary arm. Referring to Figure 2(a) this condition is represented graphically to show that the time limit of one-fifteenth of a second must .elapse before a subsequent character can be transmitted, as for example, the transmission of the character A two times successively.

It is intended to use this time period required for one unit to operate to efiectthe transmission of the impulse to a second printing telegraph unit, during which interval as mentioned the printing operation is set up. In the system referred to in 3 transmitted by the plurality of transmitting telegraph units. In the figure two combinations of transmitting and receiving units are shown to illustrate the principle of operation of the invention, it is obvious, however, that more than two units at each station may be used in a similar manner, depending upon the number of segments or contacts arranged on the common distributors, and therefore the invention is not to be limited to the specific number shown merely for illustrative purposes.

The said segments 12, as shown, for each unit are allocated on half of the distributor l5, transmitting unit T2 is connected to the distributor and transmitting devices 20 similar to the unit TI described above. Likewise at the receiving station additional segments 28 are provided on the distributor 22 for the unit R-2, so that there is one segment for every character to be received by said unit.

It was mentioned hereinbefore that rotary arm 23 driven by motor 24 was operated continuously in synchronism with the transmitting rotary arm [3, so that when a signal is transmitted from unit TI, the signal transmitted is received by its corresponding receiving unit R-l, similarly, the signal transmitted by unit T2 is received aoszaooa and recorded by its corresponding unit R-Z.

Referring now to Fig. 3, the shaded portions of the diagram indicate the time required by the recording units to efiect reception of the charac= ter impulses. v

When its corresponding transmitting unit sends out the selected character pulse in a manner described above, the receiving unit for example, R-E requires the timed interval of one-fifteenth of a second to record the character, as indicated in the figure. The character signal position is shown in the definite timed interval and it is evident that during this timed interval the unit can record this one character only. From the Fig. 2 it can be seen that a fraction of the timed interval is but necessary to transmit the signal or impulse by the transmitting distributor ill and wave transmitter it over the network, and that a plurality of such impulses could be transmitted over the network in the selected timed period.

Therefore during the printing time of unit Ri, other impulses from separate units may be transmitted, and as shown in the figure unit R2 is conditioned to receive a signal during this period. And vice versa during the printing time of R2, a signal may be set up by its correspond ing transmitting unit to be transmitted to unit -R--2 to be recorded.

In this manner a portion of the wasted cycle may be used to operate a plurality of separate units during the period other units are functionmg.

The above description illustrated the applica tion of the invention to the simultaneous transmission of a plurality of messages in one direction, however, the application is not limited to this single application, since it is feasible for du-= plex operation. to transmit a plurality" of messages in opposite directions simultaneously. Re ferring now to Fig. 4, the transmitting telegraph units T and recording units R operate in the same manner as described above and need not be re peated here. "At the transmitting station a separate transmitting and recording unit are connected to the common distributor unit Sit in the manner described, so that the rotating arm 86 engages the transmitting contacts i2 and receiv ing contacts it in succession to operate the respective units. In a like manner the units R-l and T2 at the remote station are connected to the common distributor to be operated when the rotary arm operated in synchronism with arm 3i engages its corresponding segments. For duplex operation over a radio network it is neces= sary to duplicate the wave transmission equipment at both stations as shown, which is obviously not necessary for ordinary line operation.

Referring again to Fig. 3, during the timed period during which the printing operation is set up for unit R-t, transmitting unit 'i2 is in a position to be operated to initiate a selected character impulse to be transmitted in an oppo site direction to operate its corresponding unit R2 at a later stage in the cycle.

While there has been shown and described and pointed out the fundamental novel features of the invention as applied to a single modifica tion, it will be understood that various omissions and substitutions and changes in the term and details of the device illustrated and in its opera= tion may be made by those skilled in the art with= out departing from the spirit of the invention. It is the intention therefore to be limited only as indicated by the scope of the following claims.

What is claimed is:

l. In a communication system, a transmitting and a receiving distributor, the operation of each distributor beingin timed relation with that oil the other, a plurality of transmitting and re ceiving tele-prlnting units having individual con trolling character key bars, said units associated with the said distributors, means associated with the lreybars of each of said transmitting units and its associated distributor or distributors to initiate and transmit character impulses at differential times to represent diflerent characters during a predetermined timed interval, each by a single differentially timed impulse, means associated with the key bars of the said receiving units and its associated distributor or distributors to control each receiving unit so as to record the character signals in accordance with their transmission irom the corresponding transmitting units, and means included in the said associated distributors to transmit from each transmitting unit the similar difierentially timed impulses to control the corresponding receiving units during the said predetermined timed interval required to initiate a single character impulse.

2. In a communication system, a transmitting and a receiving distributor having disposed there on a plurality of individual contact segments, the operation of each distributor being in timed relation with that of the other, a plurality of trans mitting and receiving tele-printing units, having individual controlling character key bars, the said hey bars of the units being associated with the distributor contact segments, means associated with the key bars of each of the said transmit ting units and its cooperating distributor to initiate and transmit character impulses at difierential times to represent different characters during a predetermined timed interval, each by a single difierentially timed impulse, means associated with the key bars of the said receiving units and its cooperating distributor to control each receiving unit so as to record the character sig" nals in accordance with their transmission from the corresponding transmitting units, the said individual contact segments of the transmitting and receiving distributors so arranged that the transmitting units are adapted to transmit the similar difierentially timed impulses to control the corresponding receiving units during the said predetermined timed interval required to initiate a single character impulse.

3. In a communication system, a transmitting and a receiving distributor having disposed thereon a plurality of individual contact segments, the operation of each distributor being in timed relation with that of the other, a plurality of trans= mitting and receiving tele-printing units having individual controlling character hey bars, switch ing means included in the transmitting unit and associated with the corresponding key bars to be operated thereby, electromagnetic controlling means associated with the key bars of the said receiving units, the said hey bars and switching means of the transmitting units are associated with the individual contact segments of its coop crating distributor whereby signal impulses cor-= responding to operations of said hey bars are initiated and transmitted at differential timed instances during a predetermined timed interval governed by the operation of the cooperating dis= tributor, and the said electromagnetic controlling means are associated with other individual con tact segments of its cooperating distributor where '34;

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